This is the kind of thing that linguists mean when they say that gender in languages with noun gender is arbitrary: malheur is masculine, peur is feminine; why? No reason–it’s just one of those things that you have to memorize. When a language has two genders, people will try endlessly to convince you that the specific noun genders in that language are as they should be (of course a tugboat (remorqueur) is masculine and booze (liqueur) is feminine, they might say); when a language has three genders (Bulgarian, German, Tamil) they don’t argue quite so loudly; get above 15 (Swahili: 18, Shona: 20), and you have trouble convincing those same people that they’re gender systems. And yet: the phenomena are the same whether you’re talking about the two genders of French or the 20 genders of Shona: some things have to agree with nouns. What classes do those nouns fall into? Does it really matter what we call them? No, not really.
The task of the day: memorize the gender of nouns ending with -eur. Now, I know what the native speakers are going to tell me: It’s easy, Zipf. If it’s a person, it’s masculine, and there’s a corresponding feminine form, which might end in -euse (chanteuse) or might not (doctoresse). If it’s an abstract quality—peur, douleur, fureur-–then it’s feminine, except when it’s not, like bonheur and malheur. Oh, and remorqueur is a tugboat, not a person, but it’s still masculine, plus fleur and sueur are not abstract qualities, but they’re feminine. Yep: it’s arbitrary–you just have to memorize it.
I think you can figure out how these drills work. Oh–native speakers might disagree about some of these, especially the two plurals couleurs, one for the flag and one for the darks in your laundry. Native speakers, please feel free to chime in in the Comments section…
Zipf's Law 
My fridge looks just like that with pages stuck all over it. Some days I even think it’s fun …. some days I want to drown in a vat of liqueur 🙄
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Twenty genders? I need to give that some thought.
Sorry, I just tried and discovered that I have no idea how to give it some thought. Where do I even start?
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I would come at it from the opposite angle. You have a system such that there are things–let’s say adjectives–that have to agree with nouns. There are multiple classes of such nouns, and things (let’s say adjectives) agree with them in specific ways for each class. If you don’t like calling that a gender system when there are 20 classes of nouns, or 19 classes of nouns, or 18 classes of nouns, [same for 17, 16, etc., down to 4 classes of nouns], why would we suddenly become sorta OK with calling it gender when there are 3, and see it as positively NATURAL when there are 2?
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Right. If I think of gender in this context as meaning something other than gender, my head doesn’t explode.–even when we get down to two. Perfect.
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Would you mind if I worked your question into a post at some point?
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If the question’s addressed to me (sorry–I’ve lost track of the comment/reply relationship here–I’d be delighted.
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…and indeed it WAS directed to you. 🙂
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I see I also lost track of the end parenthesis. Things’ve been like that around here lately
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